Well, .apk is essentially just a compressed container. So, any online AV scanner that also looks inside archives should work. Then it's just a matter of inclusion of Android detection signatures in a desktop product...

VirusTotal for Android checks the applications installed in your Android phone against VirusTotal (http://www.virustotal.com). It will inform you about malware (virus, trojans, worms) on your phone and allows you to upload any unknown applications to VirusTotal. In other words, VirusTotal for Android will get your applications scanned by more than 40 antivirus, flagging any undesired content.